The present disclosure relates to a load-sense system such as a load-sense steering system that operates in a static load-sense mode for low flows and operates in a dynamic load-sense mode for high flows.

Disclosed embodiments include steering circuits utilizing a controllable cross-feed loop between left and right drive motor sides of an articulated power machine to reduce skidding caused by a turning operation in which an articulation actuator changes an articulation joint angle between a front frame member and a rear frame member of the power machine.

A hydraulic system for a work machine including a first and a second hydraulic actuator, and a first and a second hydraulic machine for providing hydraulic fluid to at least one of the first and the second actuator via a first and a second priority valve, respectively. The first and second priority valves are controlled by a pressure drop P over the inlet valve of the first actuator such that when P is lower than a first threshold value T1, a flow of hydraulic fluid is allowed only to the first actuator. The second priority valve allows a flow of hydraulic fluid to both the first and second actuator for a pressure drop higher than T1. The first priority valve is further configured to allow a flow of hydraulic fluid to both of the first and second actuator for a pressure drop higher than a second threshold value T2 which is higher than T1.

A dual pressure margin priority circuit and method for controlling flow from a pump to steering valve and low priority inlets. A steering pressure valve controls flow from pump to steering valve inlets, and provides a steering valve load sense pressure. A priority valve controls flow from pump to low priority inlets. A load sense cutoff valve has a first inlet receiving the steering valve load sense pressure. The load sense cutoff valve controls flow through the priority valve based on steering valve load sense pressure at the first cutoff valve inlet. The cutoff valve can include a second inlet coupled to tank, and a load sense input coupled to the steering valve load sense pressure. The cutoff valve can be a pressure limiter valve. The priority and steering pressure valves can be 2-way proportional flow spool valves with bias springs, and contributing and opposing load sense inputs.

A hydraulic steering arrangement (2) is described having a main flow path (8) with a flow meter (9) and an amplification flow path (10) opening into the main flow path (8) at a connecting point (11) located between the flow meter (9) and a working port arrangement (L, R). Such a steering arrangement should have in a simple way a large flow of the hydraulic fluid to the working port arrangement. To this end pressure increasing means (17) are arranged in the main flow path (8) upstream the connecting point (11).

In order to provide a steering device for a construction/transport/farm machine which can be steered by means of a steering wheel operation and by means of a lever operation (or automatic steering) such that not only can a mechanism for prioritizing the steering wheel operation be achieved with a simple configuration, but the mechanism can also be caused to stably operate, the steering device is provided with: steering cylinders 1; a steering valve 2; a pump 3; a steering wheel control valve 4; an electromagnetic control valve 5 for lever/automatic steering; a steering wheel priority valve 6; and a change-over valve 7 which, upon sensing a load pressure generated when the steering wheel control valve 4 is operated, switches the setting of the steering wheel priority valve 6 by using the load pressure, wherein the change-over valve 7 for switching the setting of the steering wheel priority valve 6 has a two-port two-position configuration whereby a drain oil passage of the steering wheel priority valve 6 is closed by utilizing the load pressure generated when the steering wheel control valve 4 is operated.

An apparatus for operating a load-controlled hydraulic supply of an agricultural tractor includes a hydraulic pump which is adjustable with respect to the displacement volume for supplying pressurized hydraulic fluid, a proportional valve which is electrically actuatable, a primary hydraulic consumer to carry out a superordinate hydraulic function and to be directly connected to a conveying outlet of the hydraulic pump, a secondary hydraulic consumer to carry out a subordinate hydraulic function and to be connected to the conveying outlet of the hydraulic pump via the proportional valve, and a control unit configured to move the proportional valve into a closed valve position when the control unit recognizes that at least one of a required power of the primary and secondary hydraulic consumers exceeds the conveying capacity of the hydraulic pump and the subordinate hydraulic function of the secondary hydraulic consumer is inactive.

A hydraulic fluid supply portion of a hydraulic steering control system may include an accumulator holding a quantity of pressurized steering fluid, and a priority valve. The priority valve may have a priority supply inlet port fluidly connected to the accumulator for receiving pressurized steering fluid from the accumulator, and a priority supply outlet port fluidly connected to a steering flow amplifier circuit. The priority valve may have a normally open position with a minimal pressure drop between the priority supply inlet port and the priority supply outlet port, and a flow restriction position where fluid flow between the ports is restricted. A load signal line from a steering control circuit to the priority valve may bias the priority valve toward the normally open position in response to an operator steering command to provide pressurized steering fluid to the steering flow amplifier circuit.

A hydraulic system for a work machine comprising a priority circuit including at least a first priority actuator and a priority control valve for controlling the supply of hydraulic fluid to the first priority actuator and for providing a load sense signal indicative of the load acting on the first priority actuator; an auxiliary circuit including at least a first auxiliary actuator and at least a first auxiliary control valve for controlling the supply of hydraulic fluid to the first auxiliary actuator; at least a first pump for producing a flow of hydraulic fluid; and a priority valve for distributing the flow from the pump to the priority circuit and auxiliary circuit for operating the respective actuators thereof, with priority being given to the priority circuit as a function of the load sense signal.

The present disclosure relates to a hydraulic pump assembly comprising: a variable displacement pump, preferably a load-sensing variable displacement pump, for outputting a volume flow rate of a hydraulic fluid, an electric motor for driving the variable displacement pump, in particular a swashplate or swivel angle pump, via a variable-speed drive shaft, and a control unit which is connected to the variable displacement pump and the electric motor and is configured to provide a predetermined volume flow rate by controlling the variable displacement pump and the electric motor. The hydraulic pump assembly is characterized in that the pump assembly further comprises a temperature sensor connected to the control unit, which senses a winding temperature of the electric motor, wherein as long as the winding temperature is below a threshold, the control unit is configured to provide the predetermined volume flow rate.